U.S. patent number 7,091,968 [Application Number 09/359,561] was granted by the patent office on 2006-08-15 for method and apparatus for encoding a user interface.
This patent grant is currently assigned to Sedna Patent Services, LLC. Invention is credited to Sadik Bayrakeri, Donald F. Gordon, Edward A. Ludvig, Nathan W. Osborn.
United States Patent |
7,091,968 |
Ludvig , et al. |
August 15, 2006 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for encoding a user interface
Abstract
A method and apparatus for combining video frame sequences with
a video display of an interactive program guide (IPG). The
apparatus comprises a plurality of compositors that combine
background information, video frame sequences and program guide
graphics into a single video frame sequence. The sequence is then
digitally encoded to form an MPEG-like bitstream. The same
background information and informational video is composited with a
different program guide graphic to form another video sequence that
is also encoded. A plurality of such sequences are produced with
each sequence having a different program guide graphic. Each
sequence is encoded and then multiplexed into a transport stream
such that all the encoded sequences are transmitted to a
subscriber's terminal using a single transport stream. As such, the
subscriber can transition from one program guide to the next
without interruption of the background or video display as the
program guide graphic is changed.
Inventors: |
Ludvig; Edward A. (Redwood
City, CA), Gordon; Donald F. (Los Altos, CA), Osborn;
Nathan W. (Menlo Park, CA), Bayrakeri; Sadik (Foster
City, CA) |
Assignee: |
Sedna Patent Services, LLC
(Philadelphia, PA)
|
Family
ID: |
27492681 |
Appl.
No.: |
09/359,561 |
Filed: |
July 22, 1999 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
09293526 |
Apr 15, 1999 |
|
|
|
|
09201528 |
Nov 30, 1998 |
|
|
|
|
60093891 |
Jul 23, 1998 |
|
|
|
|
Current U.S.
Class: |
725/39;
348/E5.112; 725/41; 725/61; 725/60; 348/E7.063; 348/E7.061;
348/E5.105; 375/E7.268 |
Current CPC
Class: |
H04N
21/2365 (20130101); H04N 21/4347 (20130101); H04N
21/4821 (20130101); H04N 21/47 (20130101); H04N
21/482 (20130101); H04N 21/4532 (20130101); H04N
21/4314 (20130101); H04N 21/6547 (20130101); H04N
7/165 (20130101); H04N 21/84 (20130101); H04N
7/163 (20130101); H04N 5/45 (20130101) |
Current International
Class: |
H04N
5/445 (20060101) |
Field of
Search: |
;725/59-61,91,103,114,138,144 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tran; Hai
Assistant Examiner: Huynh; Son P.
Attorney, Agent or Firm: Patterson & Sheridan, LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims benefit of U.S. provisional patent
application Ser. No. 60/093,891 filed Jul. 23, 1998 which is hereby
incorporated herein by reference. This application is also a
continuation-in-part of commonly assigned U.S. patent application
Ser. No. 09/293,526 filed Apr. 15, 1999 and commonly assigned U.S.
patent application Ser. No. 09/201,528 filed Nov. 30, 1998, both of
which are hereby incorporated herein by reference.
Claims
What is claimed is:
1. A method of producing an encoded user interface comprising:
producing a video frame sequence representing an interactive
program guide by combining, in a frame synchronized manner,
background imagery with at least one video sequence and at least
one graphic containing program guide information to form said video
frame sequence; encoding said video frame sequence within a head
end of an information distribution system distribution system;
wherein the combining step further comprises: compositing,
frame-by-frame, at least one video sequence onto said background
imagery to form a background sequence; and compositing a plurality
of program guide graphics onto said background sequence, where a
different program guide graphic is composited onto said background
sequence to form a plurality of program guide frame sequences that
represent individual program guide pages.
2. The method of claim 1 wherein said encoding step further
comprises the step of: encoding the video frame sequence to
compress information therein to form a digital bitstream.
3. The method of claim 2 wherein said encoding step further
comprises: separately encoding each of said program guide frame
sequences to form a digital bitstream for each of the program guide
frame sequences.
4. The method of claim 3 further comprising the steps of:
multiplexing each of the digital bitstreams into a common transport
stream.
5. The method of claim 4 wherein fifteen program guide sequences
are formed, encoded, and contained in said common transport
stream.
6. The method of claim 3 further comprising: encoding an audio
signal associated with one of the video sequences; and multiplexing
the encoded audio signal into the common transport stream.
7. The method of claim 6 wherein said multiplexing step further
comprises the step of: multiplexing foreground program guide data
into said common transport stream.
8. The method of claim 1 wherein the video frame sequence is a
television program.
9. The method of claim 1 wherein the video frame sequence is an
advertising program.
10. The method of claim 1 wherein the video frame sequence is
encoded using slice based encoding.
11. The method of claim 10 wherein slice based encoding encodes
different regions in a different manner than the encoding that is
performed upon other portions of the video frame sequence.
12. The method of claim 11 wherein each region is assigned a unique
program identifier.
13. A method of producing an encoded user interface, said encoded
user interface comprising a plurality of bitstreams representing
respective interactive program guide (IPG) pages and forming
thereby a sequence of IPG pages, said method comprising: combining,
in a frame synchronized manner, background imagery with each of a
plurality of video sequences to form a plurality of IPG video
portions; overlaying a plurality of respective graphic images
containing program guide information over respective ones of each
of said plurality of IPG video portions to form a plurality of IPG
page portions, each of said plurality of IPG page portions
comprising a respective common video portion and a plurality of
programming information portions, and wherein a plurality of IPG
page sequences comprises common programming information portions
and differing video portions per IPG page sequence; encoding each
sequence of IPG pages within a head-end of an information
distribution system to form said plurality of bitstreams; providing
a unique packet identifier (PID) for each IPG page; providing an
indicator in each bitstream where said video component may be
switched from one PID to another PID; and multiplexing said
plurality of bitstreams in a common transport stream to subscriber
equipment.
14. The method of claim 13, wherein at any instance, each bitstream
comprises a different graphical component and a matching video
component.
15. The method of claim 13, further comprising forming said IPG
pages in a similar length compared to each other.
16. The method of claim 15, further comprising: identifying a
longest IPG page; inserting null packets into other IPG pages such
that all of said IPG pages are equal in length; and adding
switching packets at an end of said IPG sequence after said null
packets.
17. The method of claim 13, further comprising: buffering all
packets for all IPG pages of each sequence of IPG pages prior to
forming said transport stream; ordering packets of said IPG pages
in said transport stream, wherein said finishing at a common point;
and adding switching packets at an end of each sequence of IPG
pages.
18. The method of claim 13, further comprising: starting each IPG
page sequence together; waiting until all packets for all of said
IPG pages are generated; and inserting switching packets in said
bitstreams at a common interval and location in said bitstreams.
Description
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The invention relates to electronic program guides and, more
particularly, the invention relates to a technique for encoding a
user interface of an information distribution system.
2. Description of the Background Art
In several communications systems, the data to be transmitted is
compressed so that the available transmission bandwidth is used
more efficiently. For example, the Moving Pictures Experts Group
(MPEG) has promulgated several standards relating to digital data
delivery systems. The first, known as MPEG-1 refers to ISO/IEC
standards 11172 and is incorporated herein by reference. The
second, known as MPEG-2, refers to ISO/IEC standards 13818 and is
also incorporated herein by reference. A compressed digital video
system is described in the Advanced Television Systems Committee
(ATSC) digital television standard document A/53, and is
incorporated herein by reference.
The above-referenced standards describe data processing and
manipulation techniques that are well suited to the compression and
delivery of video, audio and other information using fixed or
variable rate digital communications systems. In particular, the
above-referenced standards, and other "MPEG-like" standards and
techniques, compress, illustratively, video information using
intra-frame coding techniques (such as run-length coding, Huffman
coding and the like) and inter-frame coding techniques (such as
forward and backward predictive coding, motion compensation and the
like). Specifically, in the case of video processing systems, MPEG
and MPEG-like video processing systems are characterized by
prediction-based compression encoding of video frames with or
without intra- and/or inter-frame motion compensation encoding.
Over the past few years, television has seen a transformation in a
variety of means by which its programming is distributed to
consumers. Cable television systems are doubling or even tripling
system bandwidth with the migration to hybrid fiber coax (HFC)
cable plant thereby offering a larger number of channels to the
viewer. Customers unsatisfied with their local cable systems have
switched in high numbers to direct broadcast satellite (DBS)
systems. And, a variety of other approaches have been attempted
focusing primarily on high bandwidth digital technologies,
intelligent two way set top boxes, or other methods of trying to
offer service differentiated from standard cable and over the air
broadcast systems.
With this increase in bandwidth, the number of programming choices
has also increased. Leveraging off the availability of more
intelligent set top boxes, several companies such as Starsight and
Prevue Guide have developed elaborate systems for providing an
interactive listing of a vast array of channel offerings, expanded
textual information about individual programs, the ability to look
forward to plan television viewing as much as several weeks in
advance, and the option of automatically programming a VCR to
record a future broadcast of a television program.
Unfortunately, the existing program guides have several drawbacks.
They tend to require a lot of memory, some of them needing upwards
of one megabyte of set top terminal (STT) memory. They are very
slow to acquire their current database when they are activated for
the first time or are subsequently restarted (e.g., a large
database may be downloaded to a STT using only a vertical blanking
interval (VBI) data insertion technique). Disadvantageously, such
slow database acquisition may result in out of date database
information or, in the case of a pay per view (PPV) or
video-on-demand (VOD) system, limited scheduling flexibility for
the information provider. The user interface to existing program
guides does not usually look like a typical television control
interface; rather looks like a 1980's style computer display (i.e.,
blocky, ill-formed text and/or graphics).
Additionally, the present program guides may provide an advertising
or preview region along with the program guide graphics. However,
the insertion of these additional video signals is performed using
an analog compositor that merely inserts (overlays) the additional
imagery into the broadcast stream. The analog compositing process
is accomplished and then the new analog video containing an
advertisement or preview and the program guide are recorded on tape
for subsequent broadcast. This compositing process is not
accomplished in real time at the head end of the cable system and,
consequently, the program guide can not contain targeted
advertising for a particular household or a particular neighborhood
or region. The program guide with its associated preview or
advertising is broadcast to all subscribers connected to the head
end of the cable system. Additionally, these program guides are
generally passive, in that, the viewer sees the program guide
information change on the screen to indicate different programs and
their associated channels. However, there is no provision enabling
a viewer to interact with the program guide display to scroll
through the channel or channels that are available. Because such
scrolling in an analog system requires a splice to a new program
guide video sequence, the program guides that are interactive do
not include advertising video or other video information with the
program guide.
Therefore, it is desirable to provide a method and apparatus for
encoding an interactive program guide.
SUMMARY OF THE INVENTION
The disadvantages associated with the prior art are overcome by the
present invention of a method and apparatus for encoding user
interface of an information distribution system. One embodiment of
such user interface is an interactive program guide (IPG) that
forms an IPG screen or page containing a graphical guide region and
a video region playing at least one video sequence. The invention
is a method and apparatus for performing ensemble encoding of one
or more IPG pages. The invention comprises a plurality of
compositors that combine background information, informational
video and program guide graphics into a single sequence of video
frames. The sequence is then digitally encoded to form an MPEG-like
bitstream. The same background information and informational video
is composited with a different program guide graphic to form
another video sequence that is also encoded. A plurality of such
bitstreams are produced with each sequence containing a different
program guide graphic. The encoding is performed using a common
coding profile and a common clock for each of the encoders. The
encoded sequences are then multiplexed into at least one transport
stream such that all the encoded sequences are transmitted to
subscriber equipment using one or more transport streams. As such,
the subscriber can transition from one program guide page to the
next without interruption of the background or informational video
as the program guide page graphic is changed.
The informational video may appear in multiple locations upon the
IPG screen. Promotional or advertising video may appear in one
portion while an animated graphic appears in another location. Each
of the informational video streams may have a different rate of
display. The encoders handle different video rates by using slice
based encoding of the composite image sequence.
One example of a program guide that is encoded in accordance with
the invention has each graphic containing a set of programs (e.g.,
channels) listed along a left, vertical axis and each program
associated with the channel is identified in a rectangular cell
that extends toward the right. The horizontal axis represents time
and about 1.5 hour of programming for ten channels is shown in each
program guide graphic page. The informational video is generally
contained in one or more regions above the program graphic.
In another example of a program guide that is encoded in accordance
with the invention has each graphic containing a set of programs
(e.g., channels) listed along a left, vertical axis and each
program associated with the channel is identified in a cell that is
listed beneath a time axis. The horizontal axis represents time and
about 1.5 hours of programming for eight channels is shown in each
program guide graphic page. Each channel is associated with text
that represents three programming slots, one for each half hour in
the time axis. The informational video is generally contained in
one or more regions next to the program graphic, i.e., a guide
region is on the left half of the screen and the video region is on
the right half of the screen or vice versa.
BRIEF DESCRIPTION OF THE DRAWINGS
The teachings of the present invention can be readily understood by
considering the following detailed description in conjunction with
the accompanying drawings, in which:
FIG. 1 depicts a high-level block diagram of an information
distribution system that uses the interactive program guide of the
present invention;
FIG. 2 depicts a block diagram of an IPG generator of the present
invention;
FIG. 3 depicts a block diagram of a compositor unit that produces
background/informational frame sequence in accordance with the
present invention;
FIG. 4 depicts a block diagram of an IPG compositor that inserts an
IPG graphic into the background/informational frame sequence;
FIGS. 5A 5C depicts a series of illustrative IPG pages;
FIG. 6 depicts another example of an IPG page that can be produced
by the invention; and
FIG. 7 depicts a PID map for a set of IPG pages encoded by the
invention.
To facilitate understanding, identical reference numerals have been
used, where possible, to designate identical elements that are
common to the figures.
DETAILED DESCRIPTION
FIG. 1 depicts a high-level block diagram of an information
distribution system 100, e.g., a video-on-demand system or digital
cable system, that incorporates the present invention. The system
100 contains service provider equipment (SPE) 102 (e.g., a head
end), a distribution network 104 (e.g., hybrid fiber-coax network)
and subscriber equipment (SE) 106. This form of information
distribution system is disclosed in commonly assigned U.S. Pat. No.
6,253,375, issued Jun. 26, 2001. The system is known as the
Onset.TM. system provided by DIVA Systems Corporation of Menlo
Park, Calif.
In general, the SPE 102 produces a plurality of digital bitstreams
that contain encoded information (e.g., television programming in
an MPEG-like compressed form). These bitstreams are modulated using
a modulation format that is compatible with the distribution
network 104. The subscriber equipment 106, at each subscriber
location 106.sub.1, 106.sub.2, . . . , 106.sub.n, comprises a
demodulator/decoder 124 and a display 126. Upon receiving a
bitstream, the subscriber equipment decoder 124 extracts the
information from the received signal and decodes the stream to
produce the information on the display, i.e., produce a television
program or program guide page.
In an interactive information distribution system such as the one
described in commonly assigned U.S. Pat. No. 6,253,375, issued Jun.
26, 2001, the program bitstreams are addressed to particular
subscriber equipment locations that requested the information
through an interactive menu. An appropriate interactive menu
structure for requesting video on demand is disclosed in commonly
assigned U.S. Pat. No. 6,208,335, issued Mar. 27, 2001.
To assist a subscriber (or other viewer) in selecting programming,
the SPE 102 produces a interactive program guide (IPG) in
accordance with the present invention. The IPG of the present
invention contains program information, e.g., title, time, channel,
program duration and the like, as well at least one region
displaying full motion video, i.e., a television advertisement or
promotion. Such informational video is provided in various
locations within the program guide screen.
FIG. 5A illustrates a first example of an IPG 500 that is produced
in accordance with the present invention. The IPG 500 contains a
background 502, a plurality of video display regions 504, 506, and
508, and a program guide graphic 510. The program guide graphic 510
contains a left (or right), vertical axis 512 representing the
available channels and a bottom (or top), horizontal axis 514
represents time. Generally, about 1.5 to 2 hours of programming are
displayed in the guide graphic 510. Each program (e.g., P1, P2, P3,
and so on) is identified by a program title within a rectangular
cell. The extent of the cell (its length) indicates the duration of
the program and the starting location of the left edge of the cell
indicates the starting time of the program. The arrangement of the
program identification cells in this manner is a conventional
arrangement in which programming guides have been organized in
print for years.
Returning to FIG. 1, the invention produces the IPG (500 of FIG.
5A) using a novel compositing technique that enables full motion
video to be positioned within an IPG and have the video seamlessly
transition from one IPG page to another. FIG. 1 depicts the
components that are necessary to produce an IPG page that contains
at least one video region. The embodiment of the invention is
described as having advertising displayed in the video region or
regions. However, advertising is merely illustrative of a type of
informational video and any sequence of video or graphic
information can be displayed in these regions. To this end, the SPE
102 contains a video storage device 108, an informational video
selection and monitoring system 110, an IPG generator 116 (an
ensemble encoder), a background storage device 118, a controller
114, an IPG grid generator 120, and a digital video modulator 122.
The video selection and monitoring system 110 controls timing of
the informational video display and, if the video is an
advertisement, tracks video utilization to facilitate billing to an
advertiser whenever a particular advertisement is transmitted.
Thus, the video selection and monitoring system 110 requests that
the storage device 108 (e.g., a disk drive or magneto-optical
drive) recall and send to the IPG generator 116 a particular video
sequence. The video is stored in the storage device 108 as
frame-based digital video (i.e., 601 format video) and associated
audio. Alternatively, compressed or uncompressed analog video as
well as other formats of video information may be stored in the
storage device 108. These formats are converted to 601 format prior
to sending the video to the IPG generator 116.
As the video is recalled from device 108, each video sequence is
coupled to the IPG generator 116. As such, three video streams and
one audio stream (e.g., an audio stream associated with one of the
advertisements) are provided to the IPG generator 116.
Additionally, a background image is recalled from the storage
device 118 under instructions from the controller 114. The
background image is generally a static graphic, but it may be a
video frame sequence containing moving imagery. Lastly, the IPG
grid generator 120 provides a program guide graphic to the IPG
generator 116. The IPG data for the graphic can be provided from
any one of a number of sources such as a network cable feed, an
internet site, a satellite feed, and the like. The guide program
data is formatted, for example, into the rectangular grid graphic
of program cells (screen 500 of FIG. 5A) by the IPG grid generator
120. As shall be discussed below with respect to FIG. 6, other IPG
page layouts may be used and are considered to be within the scope
of this invention.
The IPG generator 116 performs ensemble encoding by combining the
three video sequences, the background and the guide graphics into a
comprehensive IPG display such as the one depicted as IPG page 500
in FIG. 5A or IPG page 600 in FIG. 6. As shall be described in
detail below, the informational video is overlaid onto the
background to form a background/video composite and then various
IPG grids are overlaid upon the background/video composite. In this
manner, a number of IPG "pages", for example, fifteen of them, are
produced, where each page depicts ten channels of programming
information. Each of these IPG pages is encoded within the IPG
generator 116 into a compressed digital bitstream, e.g., an MPEG
compliant bitstream. The bitstream is then modulated by the digital
video modulator 122 using a modulation format that is compatible
with the distribution network 104. For example, in the OnSet.TM.
system the modulation is quadrature amplitude modulation (QAM);
however, other modulation formats could be used.
The subscriber equipment 106 contains a demodulator/decoder 124 and
a display 126 (e.g., a television). The demodulator/decoder 124
demodulates the signals carried by the distribution network 104 and
decodes the demodulated signals to extract the IPG pages from the
bitstream. As shall be described below, each of the IPG pages is
identified with a unique program identification code (known as a
PID) that is used by the demodulator/decoder 124 to select a
bitstream for decoding. The decoded IPG page is displayed, as shown
in FIG. 5A, to the subscriber or viewer. As the viewer selects
another IPG page containing other program information, generally by
scrolling to the bottom of the IPG graphic 510 using a remote
control interface 128 or some other input device, the IPG page
stream associated with the next PID is decoded. The only change the
viewer sees is the IPG graphic changes (from, for example, graphic
510.sub.1 to 510.sub.2), the informational video and its associated
audio seamlessly continues playing. This seamless play occurs
because each of the IPG pages contains the same, frame synchronized
background and informational video and only the IPG graphic changes
from page to page. As such, the decoder seamlessly transitions from
one IPG page to another.
FIG. 2 depicts a block diagram of the IPG generator 116. The IPG
generator 116 contains a compositor unit 200, a plurality of IPG
grid compositors 202, a plurality of video encoders 204 (e.g.,
MPEG-2 compliant encoders), a common profile and clock generator
250, a transport stream multiplexer 206, an audio delay 208, an
audio encoder 210 (e.g., an Dolby AC-3 audio encoder) and the IPG
grid generator 120. The compositor unit 200 positions the
informational video sequences (vs2, vs3, vs4) upon the background
video imagery (vs1). To facilitate positioning, the controller (114
in FIG. 1) provides the compositor unit 200 with the coordinates of
one corner of each informational video and provides a size
indicator for each rectangular region in which the video will be
displayed relative to the background. The compositor unit 200
performs the placement and fusing of the imagery to form
background/information video frame sequence. Further detail of this
compositing process is provided below with respect to FIG. 3.
The composite image (e.g., three, full motion video frame sequences
positioned upon a background image, the background/informational
video) is coupled to a plurality of IPG grid compositors 202.sub.1,
202.sub.2, 202.sub.3, . . . , 202.sub.15 (collectively referred to
as compositors 202). The compositors 202 combine the respective IPG
graphics with the background/informational video combination to
produce a plurality of video frame sequences containing a composite
of the background, the informational video, and the IPG graphics.
There is one frame sequence for each IPG graphic, e.g., fifteen
sequences in all. As discussed previously, the IPG graphic is
produced by the IPG grid generator 120. The IPG grid generator 120
actually produces two items, one is the IPG grid background image
(the IPG grid graphic discussed above and shown as graphic 510 in
FIG. 5A), and IPG grid foreground overlay graphic data that is used
to generate highlighting and other special effects in the displayed
IPG screen. Additionally, this data attributes functionality to the
highlighted elements such as selecting another IPG page, selecting
a program to view, exiting the system, and the like. These special
effects and functionality are discussed below with respect to FIGS.
5A, 5B and 5C.
Each of the frame sequences (IPG screen sequences V1, V2, V3, . . .
, V15) are coupled from the compositors 202 to the plurality of
video encoders, e.g., real time MPEG-2 encoders 204.sub.1,
204.sub.2, 204.sub.3, . . . 204.sub.n (collectively encoders 204).
Each encoder 204 encodes an IPG screen sequence to form a
compressed video bitstream, e.g., an MPEG-2 compliant bitstream.
The encoders use a common encoding profile and common clock
supplied by the encoding profile and clock generator 250. As such,
each sequence of IPG frames are synchronously encoded in the same
manner.
The IPG grid foreground overlay graphics data is also coupled to
the multiplexer 206 from the IPG grid generator 120. This graphics
data is generally sent as "user data" or "private data" within the
transport stream. Further discussion of the graphics data is
provided below.
If the informational video in each IPG page have differing amounts
of motion, the encoders can encode the video in a slice-based
manner. As such, each frame is divided into a plurality of
horizontal stripes of macroblocks. Each frame contains stripe start
and stop identifiers. The information (pixels and/or macroblocks)
between the start and stop indentifiers can be encoded in a
different manner than other portions of a given stripe.
Consequently, a two dimensional region comprising portions of
adjacent stripes can be encoded differently from other portions of
the frame. The encoded information from the two dimensional region
forms a bitstream that is identified by its own program identifier.
At the subscriber equipment, the demodulator/decoder decodes the
information in each slice, then reassembles the frame by placing
the decoded slices into appropriate locations as identified by the
slice start/stop identifiers. The two dimensional regions can be
specified to align with the informational video such that the
regions can contain video having different motion, i.e., fast
versus slow motion. Consequently, one region could contain a slow
moving animated character while another region could contain a fast
moving sporting event promotion and both regions would be coded and
decoded accurately.
All the compressed video streams (E1, E2, E3, . . . , E15)
containing program guide information are multiplexed into a
transport stream using multiplexer 206. These compressed video
streams may contain the stripe-based encoded streams as well. In
addition to the video information, audio information associated
with one of the informational videos is also encoded and supplied
to the multiplexer 206. The audio signal is delayed in audio delay
208, then encoded in the audio encoder 210. The delay compensates
for the time required to perform video encoding of the associated
video vis-a-vis the audio encoding. The compressed audio data is
coupled to the multiplexer 206 for incorporation into the transport
stream.
A transport stream, as defined in ISO standard 13818-1 (commonly
known as the MPEG-2 Systems specification), is a sequence of equal
sized packets, each 188 bytes in length. Each packet has a 4-byte
header and 184 bytes of data. The header contains a number of
fields, including packet identification number (PID). The PID field
contains 13 bits and uniquely identifies each packet that contains
a portion of a "stream" of video information as well as audio
information and data. As such, to decode a particular video
bitstream (or audio bitstream or data) for viewing, the decoder in
the subscriber equipment extracts packets containing a particular
PID and decodes those packets to create the video (and audio) for
viewing.
Each of the fifteen bitstreams representing the IPG page sequences
within a particular transport stream are uniquely identified by a
PID. In the preferred embodiment, fifteen PID's are multiplexed
into a single transport stream. Certainly, less of more IPG
bitstreams can be included in a transport stream as bandwidth
permits. Additionally, more than one transport stream can be used
to transmit the IPG bitstreams. For example, additional IPG pages
may be encoded that represent additional time within a day or
additional channels. The bitstreams representing the additional IPG
pages are transmitted in additional transport streams. As such,
many IPG pages representing 24 hours of programming on hundreds of
channels can be broadcast to the subscriber equipment for selective
display to a viewer.
FIG. 7 depicts a graphical representation of PID assignment to each
IPG page. The graph 700 contains a PID axis 702 and a time axis
704. At time 1 (t1) and, more than likely, within a single
transport stream, the graphics 706 for a first IPG page and the
video 708 for a first IPG page are sent in PID1. Then, in PID2, the
graphics 710 for a second IPG page and the video 708 for the second
IPG page are sent. Note that the video is the same in each IPG page
that is sent at time 1 and only the graphics (g.sub.1, g.sub.2 . .
. g.sub.15) change from IPG page to IPG page. The change in
graphics may represent either different time intervals or different
channel groupings shown in the IPG pages. In time 2, the grouping
and encoding is repeated using different video. The process is
repeated until all the IPG pages are generated to cover all
available channels over a 24 hour period. The transport streams
carrying the encoded IPG pages are then broadcast to all
viewers.
An exemplary transport stream consists of N programs multiplexed
together into one transport stream. Each program has it's own video
PID, which contains all the MPEG bits for a single guide page. All
the programs share the same audio and PCR.
To change pages in the guide, it is required to switch between
programs (video PIDs) in a seamless manner. This cannot be done
cleanly using a standard channel change by the STT switching from
PID to PID directly, because such an operation flushes the video
and audio buffers and typically gives half a second blank
screen.
To have seamless decoder switching, a splice countdown (or random
access indicator) method is employed at the end of each video
sequence to indicate the point at which the video should be
switched from one PID to another.
Using the same profile and constant bit rate coding for each
encoding unit, the generated streams for different IPG pages are
formed in a similar length compared to each other. This is due to
the fact that the source material is almost identical differing
only in the characters in the guide from one page to another. In
this way, while streams are generated in close lengths, they are
not exactly the same lengths. For example, for any given sequence
of 15 video frames, the number of transport packets in the sequence
varies from one guide page to another. Thus a finer adjustment is
required to synchronize the beginnings and ends of each sequence
across all guide pages in order for the countdown switching to
work.
The invention provides the act of synchronization of a plurality of
streams that provides seamless switching at the STT.
Three methods are provided for that purpose:
First, for each sequence you can count the longest guide page for
that particular sequence, and then add sufficient null packets to
the end of each other guide page so that all the guide pages become
the same lengths. Then add the switching packets at the end of the
sequence, after all the null packets.
The second method requires buffering of all the packets for all
guide pages for each sequence. If this is allowed in the considered
system, then the packets can be ordered in the transport stream
such that the packets for each guide page appear at slightly higher
or lower frequencies, so that they all finish at the same point.
Then the switching packets are added at the end of each stream
without the null padding.
A third method is to start each sequence together, and then wait
until all the packets for all the guide pages have been generated.
Once the generation of all packets is completed, switching packets
are placed in the streams at the same time and point in each
stream.
Depending on the implementation of STT decoder units and
requirements of the considered application, each one of the methods
can be applied with advantages. For example, the first method,
which is null-padding, can be applied to avoid bursts of N packets
of the same PID into a decoder's video buffer faster than the MPEG
specified rate (e.g., 1.5 Mbit).
The same principles of splicing and synchronization techniques are
applicable to a plurality of different transport stream forms,
including recombinant stream.
The teachings of the above three methods can be extended apply to
similar synchronization problems and to rive similar methods.
Returning to FIG. 1, the transport stream is coupled to a digital
video modulator 122 where it is modulated onto a carrier that is
appropriate for transmission through the distribution network 104.
For a hybrid fiber coax based distribution network 104, the
modulation is quadrature amplitude modulation (QAM).
The subscriber equipment 106 is connected to the network 104 and
receives the transport stream from the network 104. A
demodulator/decoder 124 in each of the terminals extracts the
transport stream from the modulation, demultiplexes the bitstreams
within the transport stream, and decodes a selected program guide
video sequence. Since the program guide bitstreams are contained in
the transport stream, the terminal selects a particular program
guide using its unique packet identifier (PID) that causes a video
demodulator/decoder 124 to decode the program guide bitstream
identified by that PID (or PIDs in the case of slice based
encoding). When the user selects another program guide, another
stream is decoded based upon the newly selected PID or PIDs. By
transmitting many program guide streams in a common transport
stream and by frame locking the program guide source, encoding and
decoding processes, the latency experienced as a subscriber selects
one guide page after another is undetectable. Also, because the
informational video is the same and frame synchronized in each
program guide bitstream with the only difference being a different
guide graphic, the subscriber sees a transition in the guide
graphic, but the informational audio and video is seamlessly
presented to the viewer.
FIG. 3 depicts a detailed block diagram of the compositor unit 200.
The compositor unit 200 contains a plurality of serial-to-parallel
converter modules 300 and 304, a plurality of image compositors
302, 306, and 308, an optional parallel-to-serial converter module
310 and a PCI bus 312. The informational video signals vs2, vs3,
vs4 are assumed to be supplied as a conventional pixilated video
signal in a 601 format (digital video) having each frame of 601
video synchronized with the frames of the other advertisement video
signals. Generally, 601 video is supplied as a serial bitstream
that is converted into parallel stream, i.e., one complete video
frame is coupled to the compositor at a time.
More specifically, the background imagery vs1 and the first
informational video vs2 are coupled to the serial-to-parallel
converter module 300. The frames of each of these video signals are
then coupled to the compositor 302. In operation, the compositor
302 synchronizes the frames, resizes the informational video to fit
into a predefined rectangular region, positions the rectangular
region on the background and merges the two video frame sequences.
The controller 114 of FIG. 1 uses the PCI bus 312 to instruct the
compositor as to the size of the informational video region and its
position on the background. A commercially available compositor is
used to perform the foregoing operations using 601 video
signals.
The composited video sequence containing the background and first
informational video is then coupled to the second compositor 306
such that the second informational video is composited onto the
background and first video. The third compositor 308 performs a
similar function to produce a frame sequence having the background
and three informational video sequences composited into a single
sequence. The size and position of the informational video display
regions is controlled by signals from the controller via the PCI
bus 312. The output sequence from the third compositor 308 is
optionally coupled to the parallel-to-serial converter module 310
to produce a serial bitstream. Generally, the parallel data is
coupled directly to the IPG grid compositors (202 in FIG. 2);
however, if the compositor unit 200 is not physically near the
compositors 202, then the parallel-to-serial converter 310 may be
used to improve the integrity of the data as it is communicated
over a distance. Although only three informational videos were
added to the background using three compositors, clearly more
compositors can be used if additional informational video sequences
are desired.
FIG. 4 depicts a block diagram of one of the IPG grid compositors
202, e.g., compositor 2021. The compositor 2021 contains an alpha
framestore 400, a video framestore 402 and a compositor 406. The
alpha framestore 402 stores a bitmap array of weighting functions
that control the degree of transparency that the IPG grid will have
with respect to the background/informational frame sequence, i.e.,
the bitmap contains a value of transparency for each and every
pixel in the IPG graphic. As such, the alpha framestore information
controls the amount of background/advertising video scene that can
be viewed "through" the IPG graphic. The video frame store 402
buffers the IPG graphic on a frame-by-frame basis to ensure
alignment with the background/informational video frames. The
compositor 406 combines the IPG graphic with the
background/informational frames produced by the compositor unit 200
in FIG. 2. The position and size of the IPG graphic with respect to
the background is controlled, via the control signal coupled to the
compositor 406, by the controller 114 of FIG. 1.
Each of the IPG graphics, e.g., fifteen, are separately composited
in this manner with the background and the advertising. As such,
fifteen separate bitstreams, one contains each IPG graphic, are
encoded and arranged in the transport stream.
FIG. 5A depicts a first illustrative IPG page layout 500.sub.1 as
decoded by the decoder of the subscriber equipment. The page 500 is
one of the fifteen available screens (collectively referred to as
IPG pages 500) that can be decoded by appropriate selection of a
screen PID within a transport stream. Similar IPG screens can be
also decoded from other transport streams that are broadcast to the
subscriber equipment from the head end equipment. As decoded, the
informational video in regions 504, 506 and 508 plays as any
decoded video streams. The audio signal associated with one of the
informational video sequences also is decoded and plays in
conjunction with the video (i.e., audio follows video). The first
IPG graphic 510 contains, for example, program information
concerning channels 1 through 10. The subscriber, by manipulating
an input device, can scroll through the program selections. As the
scrolling function transitions from one cell to another, the cell
is highlighted by a change in the on-screen display graphics. These
graphics are sent to the subscriber equipment as "user data" and/or
"private data" within the transport stream. A detailed description
of the operation of the IPG 500 is presented in commonly assigned
U.S. patent application Ser. No. 09/359,560, filed on Jul. 22, 1999
and herein incorporated by reference.
When the subscriber reaches the bottom of the IPG graphic, i.e.,
the last cell or a special icon (arrow), a different PID is
selected for decoding, i.e., the PID for the next IPG page
containing channels 11 through 20. The decoder begins decoding the
next stream as soon as it is selected. The connection between IPG
pages is a functional attribute that is generally transmitted to
the subscriber equipment as user data within the transport stream.
Since the background and the informational video were synchronously
added to the video sequence that become the IPG pages, the
informational video seamlessly transitions from one screen to
another without any visible anomalies. The IPG graphic is the only
portion that changes from 510.sub.1 to 510.sub.2. The process of
transitioning from one IPG page to another can be accomplished by
incrementing or decrementing through the IPG pages. Additionally,
parallel pages may be available to display additional time slots.
As such, IPG pages representing programming in other time periods
could be accessed by, for example, left and right arrows. These
parallel pages may be carried in additional transport streams or in
the same transport stream.
A second illustrative IPG page layout 600 is shown in FIG. 6. This
IPG page layout is encoded in the exact same manner as the layout
500 of FIGS. 5A 5C. The IPG of FIG. 6 operates in a similar manner
to that of IPG layout 500. The layout 600 is divided vertically
such that the informational video, e.g., a video barker, appears on
the right half of the layout and the guide region appears on the
left. The guide graphics, graphical icons, background imagery, and
informational video are combined and then encoded in the same
manner as discussed above. A detailed description of the IPG 600 is
presented in commonly assigned U.S. patent application Ser. No.
09/359,560, filed on Jul. 22, 1999 and herein incorporated by
reference.
Although the foregoing description illustratively disclosed
encoding an IPG page, the invention finds use in encoding any form
of mixed graphical and video information screens. For example, the
invention can be used to encode a HTML web page in the graphics
region and a related television program in the video region.
Alternatively, the informational video can be a television program
that is displayed within a program guide while a viewer reviews the
schedule information. Selecting the video region would enlarge the
video to the entire screen, while selecting a program title in the
program guide may initiate a preview video to play in second video
window. As such, the invention should be interpreted as
encompassing any combination of video and graphics that is encoded
as a digital bit stream and broadcast from a head end of an
information distribution system.
Although various embodiments which incorporate the teachings of the
present invention have been shown and described in detail herein,
those skilled in the art can readily devise many other varied
embodiments that still incorporate these teachings.
* * * * *